21611123 has 4 divisors (see below), whose sum is σ = 22308288. Its totient is φ = 20913960.

The previous prime is 21611087. The next prime is 21611143. The reversal of 21611123 is 32111612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21611123 is a prime.

It is a super-2 number, since 2×21611123² = 934081274642258, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21611143) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 348536 + ... + 348597.

It is an arithmetic number, because the mean of its divisors is an integer number (5577072).

Almost surely, 2^21611123 is an apocalyptic number.

21611123 is a deficient number, since it is larger than the sum of its proper divisors (697165).

21611123 is an equidigital number, since it uses as much as digits as its factorization.

21611123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 697164.

The product of its digits is 72, while the sum is 17.

The square root of 21611123 is about 4648.7765057056. The cubic root of 21611123 is about 278.5431258807.

Adding to 21611123 its reverse (32111612), we get a palindrome (53722735).

The spelling of 21611123 in words is "twenty-one million, six hundred eleven thousand, one hundred twenty-three".